Question: Simplify to lowest terms. $\dfrac{30}{21}$
What is the greatest common factor (GCD) of 30 and 21? $30 = 2\cdot3\cdot5$ $21 = 3\cdot7$ $\mbox{GCD}(30, 21) = 3$ $\dfrac{30}{21} = \dfrac{10 \cdot 3}{ 7\cdot 3}$ $\hphantom{\dfrac{30}{21}} = \dfrac{10}{7} \cdot \dfrac{3}{3}$ $\hphantom{\dfrac{30}{21}} = \dfrac{10}{7} \cdot 1$ $\hphantom{\dfrac{30}{21}} = \dfrac{10}{7}$